1. Field of the Invention
The present invention relates to a gate valve capable of opening, closing, and sealing an opening portion of a vacuum process chamber used in for example the manufacturing process of a semiconductor device.
The present invention also relates to a cylinder apparatus suitable for driving a gate valve etc., more particularly relates to a cylinder apparatus suitable for driving a gate valve capable of opening, closing, and sealing an opening portion of a vacuum process chamber.
2. Description of the Related Art
In a dry etching step, sputtering step, epitaxial wafer forming step, etc. in the manufacturing process of a semiconductor device, use has been made for example of a vacuum process apparatus of a multi-chamber structure comprising a plurality of vacuum process chambers connected with each other as shown in FIG. 1.
In the vacuum process apparatus 101 illustrated in FIG. 1, a plurality of vacuum process chambers 105 for performing various processing are connected to the outer circumference of a transport chamber 102 to and from which a wafer W is transported. Movement of the wafer W between the transport chamber 102 and each vacuum process chamber 105 is carried out through a gate G. The opening, closing, and sealing of the gate G are carried out by a not illustrated gate valve.
In the illustrated vacuum process apparatus 101, the wafer W is transported into the transport chamber 102 by a transport device (not illustrated) through an inlet and outlet port 103 of an inlet and outlet path 104 and held by a vacuum transport robot 107 provided in the transport chamber 102. When the wafer W is held by the vacuum transport robot 107, the inlet and outlet port 103 is closed and the interior of the transport chamber 102 is evacuated. At this time, the gate valves are made to seal the gates G. When the evacuation of the transport chamber 102 is completed, the gate valves are driven to open the gates G, and the wafer W is transported to a predetermined vacuum process chamber 105 by the vacuum transport robot 107. In order to perform processing such as dry etching in the vacuum process chamber, the gate valves are driven to close the gates G, and predetermined processing such as dry etching is carried out on the wafer W. When the predetermined processing of the wafer W is completed, the gate valves are driven to open the gates G, and the wafer W is taken out of the vacuum process chamber 105 again by the vacuum transport robot 107 and automatically taken to the outside of the vacuum process apparatus 101 through the inlet and outlet port 103.
As a gate valve capable of opening, closing, and sealing the gate G in the vacuum process apparatus 101 as described above, for example a gate valve having a cross-sectional structure shown in FIG. 2 and FIG. 3 has been known.
In FIG. 2, a transport chamber 202 corresponding to the transport chamber 102 of FIG. 1 is connected with a vacuum process chamber 203 corresponding to the vacuum process chamber 105 of FIG. 1 through the gate G. The opening and closing of this gate G are carried out by a gate valve 201. The gate valve 201 has a valve body 205 performing opening, closing, and sealing of the gate G, a valve rod 206 to one end portion of which this valve body 205 is fixed, which is held so that it can move straight, and which can be inclined about a predetermined axis 208, a seal bellows 207 for sealing between the transport chamber 202 and the valve rod 206, and a not illustrated driving means for moving the valve rod 206 straight and inclining it.
The gate valve 201 illustrated in FIG. 2 is shown in a state where the gate G is opened. In order to close and then seal the gate G, as shown in FIG. 3, the valve rod 206 is moved straight and then moved up to a position at which the valve body 205 closes the gate G and the valve rod 206 is inclined about the axis 208. As a result, the valve body 205 presses against an O-ring 204 provided at the outer circumference of the gate G and seals the gate G.
In the gate valve 201 having the above structure, it is required that the sealing property when sealing the gate G by the valve body 205 be good, that there be no sliding part generating particles due to friction with the valve body 205 and the valve rod 207 provided in the transport chamber 202, that the movement of the valve body 205 by the not illustrated driving means be smooth and possible at a high speed, that the force for inclining the valve body 205 for crushing the O-ring 204 in order to secure a sufficient seal be sufficient, that the structure be simple and inexpensive, and so on.
In the gate valve 201 having the above structure, however, in order to perform the straight movement and inclination of the valve rod 207, sufficiently obtain a force for inclining the valve body 205, and operate the valve body 205 smoothly and at a high speed, the structure of the driving means for driving the valve rod 207 becomes complex. As a result, there are the disadvantages that the number of parts becomes large and the gate valve 201 becomes expensive.
A cylinder driven by compressed air (hereinafter referred to as an air cylinder) is usually used for driving the valve rod 206 of the gate valve 201 of the above structure. When an air cylinder is used for driving the valve rod 206, when the valve rod 206 is inclined so as to press against the O-ring 204, a moment will act upon the air cylinder from the valve rod 206 as a reaction force. However, usually, an air cylinder is not structured to be able to support a large moment applied to a piston rod. An air cylinder not structured to be able to support a large moment applied to a piston rod has the disadvantage that if the moment is repeatedly applied to the piston rod, wear and fatigue are apt to occur in constituent parts such as the piston, cylinder, and sealing member and there is insufficient durability with respect to moment.